I. Field of the Invention
This invention relates generally to non-contaminating pressure transducer modules, and more particularly relates to a pressure transducer module that effectively operates within Ultra High Purity (UHP) processing equipment that utilize UHP chemicals and require UHP conditions. The pressure transducer module of the present invention provides a continuous measurement of the pressure within a fluid flow circuit of the UHP processing equipment without contaminating the fluid within the circuit. An isolation member which  isolates a pressure sensor from the chemically corrosive fluid flow. The pressure sensor adjoins the isolation member without compromising the accuracy of the pressure measurement or increasing the risk of fluid contamination. The isolation member may be interchangeable and eliminates the need to submerge the pressure sensor in an oil or other fluid, thereby eliminating potential contaminants to the fluid flow channel.
II. Discussion of the Related Art
Over the years, the processing equipment used during the manufacture of semiconductor substrates has evolved, attempting to isolate the substrate from the presence of any small particles, metallic ions, vapors or static discharge in the environment during the manufacturing process. The processing equipment may be used to manufacture, for example, a wafer, LCD, flat panel display, and/or memory disks. Significantly, industry standards require ultra high purity environments within the processing equipment.
During the processing of semiconductor substrates, the substrate is commonly subjected to chemically corrosive fluids and high temperatures. These fluids are delivered and removed from the substrate by the UHP processing equipment through fluid lines. The various components of the processing equipment are commonly designed to reduce the amount of particulate generated and to isolate the processing chemicals from contaminating influences. Typically, the processing equipment will include monitoring and sensing devices connected in a closed loop feedback which are used in monitoring and controlling the equipment. These monitoring and sensing devices must also be designed to eliminate any contamination which might be introduced and must operate with accuracy through a wide range of temperatures.
A highly corrosive environment may be created when aggressive processing chemicals are delivered to the processing equipment. Liquid transporting systems carry these chemicals from supply tanks through pumping and regulating stations and through the processing equipment itself The liquid chemical transport systems, which includes pipes, tubing, valves, and fittings, are frequently made of plastics resistant to the deteriorating effects of the aggressive processing chemicals. Of course, anything mechanical is subject to potential leakage and such leakage can create extremely hazardous conditions both to the processing of semiconductor wafers or other products and also to personnel who may have to tend and maintain the processing equipment. Hence, the chemical transport system must be designed to detect and avoid such leakage.
Monitoring and sensing devices are incorporated into the UHP processing equipment to detect, for example, this leakage. The monitoring and sensing devices may incorporate sensors which also must be designed to avoid the introduction of particulate, unwanted ions, or vapors into the processing steps. Monitoring the pressure within the chemical transport system is useful for several reasons. First, a change in pressure within the system may indicate leakage within the system. Second, the pressure within the transport system is regulated to avoid exceeding predetermined safety limits. Third, the pressure within a fluid flow circuit may be controlled to actuate various processing tools connected to the processing equipment.
When highly corrosive hazardous chemicals are used, such corrosive atmospheric environments are extremely hard on the monitoring and sensing equipment. Further, the monitoring and sensing equipment may transmit wafer damaging particulate, ions, or vapors as a result of exposure to the corrosive atmospheric environment. Metals, which are conventionally used in such monitoring devices, cannot reliably stand up to the corrosive environment for long periods of time. Hence, the monitoring and sensing devices must incorporate substitute materials. Significantly, a mere substitution of materials in the monitoring device oftentimes produces a device with other deficiencies, including leaks and inoperativeness. Although pressure sensors have generally been developed for use in other applications, these sensors are not particularly well suited for use in semiconductor substrate UHP processing equipment. Exemplary of such a fluid pressure sensor are the pressure gauges disclosed by Schnell in U.S. Pat. No. 4,192,192 and Zavoda in U.S. Pat. No. 3,645,139. The sensing portion of the pressure gauge of the ""192 and ""139 devices are contained within a housing that requires a cavity filled with a sensor fluid or oil. The cavity is formed adjacent the fluid flow and separated by a protective member. The protective member is described by Schnell ""192 as being made from a metal having a TEFLON(copyright) coating being applied thereto. TEFLON(copyright) coatings are permeable and allow small amounts of fluid to permeate through the coating. When subjected to chemically corrosive fluids used in semiconductor substrate processing equipment, the processing fluids permeate through the coating of the protective member, corrode the metal and permeate back through the coating thereby contaminating the processing fluids. This contamination is not acceptable in UHP processing equipment. Further, it is believed that the stiffness of the metal coated ""192 protective member decreases the accuracy and resolution of the measured pressure. Hence, use of the sensors disclosed in the ""192 and ""139 patents are not acceptable in the UHP processing equipment.
The protective member of the Zavoda ""139 device is described as a TEFLON(copyright) molded single-unitary structure having a wavelike cross-section to enhance the flexibility and displacement characteristics of the diaphragm. TEFLON(copyright) films and molded parts are also permeable and allow small amounts of fluid to permeate through the part. Thus, when positioned in-line within the fluid flow circuit of semiconductor substrate processing equipment, the sensor fluid or oil contained within the housing of Zavoda would permeate through the protective member and contaminate the fluid within the fluid flow circuit. Also, a diaphragm having a wavelike cross-section as described by Zavoda ""139 is believed to decrease the accuracy of pressure measurements when measured over a wide range of temperatures. Significantly, Zavoda does not describe a diaphragm that adjoins an enclosed sensor. Further, it is believed that adjoining the sensor to the diaphragm disclosed by Zavoda would result in an inoperable or unreliable pressure sensor having minimal accuracy and resolution. Hence, there is a need for a chemically inert pressure sensor module that isolates the sensor from the fluid flow without affecting the accuracy of the pressure measurements or requiring sensor fluid.
A device in accordance with the teachings of either the ""192 or ""139 patent includes additional shortcomings when used in semiconductor substrate processing equipment. The fluid contained within a cavity of the pressure gauge of these devices is typically a silicone oil. A change in pressure within the fluid flow of the processing equipment affects the oil pressure within the cavity of these devices. Also, the oil within the cavity typically has large thermal expansions which cause large deflection changes in the protective member. The large deflection changes in the protective member increases the likelihood that the oil within the cavity will leak into the fluid flow, contaminating the flow circuit of the processing equipment. Also, the accuracy of the pressure gauge is negatively affected by the large thermal expansions of the oil. Hence, a need exists for an in-line pressure gauge that does not leak contaminating fluids into or out of the fluid flow circuit. Also, a need exists for an in-line pressure sensor, wherein the accuracy is not affected by thermo changes within the fluid flow circuit.
Other devices have been described for measuring a pressure within a fluid flow circuit. For example, Ridenour in U.S. Pat. No. 5,063,784 and Sorrell in U.S. Pat. No. 5,183,078 describe devices that may be connected in-line within a fluid flow circuit to measure the pressure therein. Each device includes a check valve which functions as a barrier between the fluid flow circuit and a remote pressure sensor. When the valve is opened, fluid from the circuit flows through the valve and a certain amount of contaminating back flow results. Thus, the devices disclosed by Sorrell and Zavoda are not suitable for use in environments where high purity is desired.
Collins et al., in U.S. Pat. No. 5,316,035 (the ""035 patent) describes a device that appears suitable for use in highly corrosive environments where high purity is desired. Collins describes a capacitance proximity monitoring device that detects the presence of liquids in the environment. The capacitance proximity device determines the change of electrical characteristics within a predetermined area as various fluids flow past the predetermined area. The changes in current from the sensing field is utilized to detect the presence of liquids within the sensing field. Although utilizable in high purity environments, the ""035 patent does not describe a device capable of measuring pressure within a fluid flow conduit of the processing equipment.
Therefore, a need exists for a non-contaminating pressure transducer which may be positioned within a fluid flow circuit carrying corrosive materials, wherein the pressure transducer determines either a gauge pressure or absolute pressure of the fluid flow circuit with a reliable resolution and accuracy. A need also exists for a pressure transducer that avoids the introduction of particulate, unwanted ions, or vapors into the flow circuit. The present invention overcomes these and other disadvantages of the related art.
The purpose of the present invention is to provide a pressure transducer module that effectively operates within a fluid flow circuit of UHP processing equipment over a wide range of temperatures with minimal affects on the accuracy and resolution of the pressure measurement without requiring sensor fluids. The pressure transducer module of the present invention may be coupled to a flow circuit of corrosive fluid, wherein either the gauge pressure or absolute pressure within the flow circuit is determined.
The various embodiments of the pressure transducer module include a pressure sensor that is both contained within a non-contaminating body and isolated from the fluid flow. In the preferred embodiment, the components of the pressure transducer module include a chemically inert housing, a cap, an integrated circuit, an isolation member or planar disc, a pressure sensor, and sealing members. The cap of the housing is removably attached to the housing. The cap or cover may include mating threads formed on an internal surface of the cover and on the external surface of the housing. An electrical connector may be mounted into the cover and electrically coupled to the integrated circuit, providing an efficient electrical connection between the integrated circuit and external connector.
The isolation member and pressure sensor are retained within the cavity by a combination of spacer and hold down rings. The hold down ring may have threading formed on its surface that mates with threading formed on the internal surface of the valve body defining the cavity. As will be described in greater detail below, the spacer ring transfers a force from the hold down ring against the isolation member and housing to seal the isolation member to the housing. In addition, an external ring with a low coefficient of expansion may be engaged against an external surface of the housing to reduce expansion of the housing proximate the points of contact between the isolation member or planar disc and the housing.
The housing, isolation member, sealing members, spacer ring, and hold down ring are preferably constructed of the same polymer to avoid leakage when the transducer is subject to thermal expansion. Without any limitation intended, chemically inert polymers of suitable known construction including fully fluorinated fluorocarbon polymers (including peifluoroalkoxy (PFA), polytetrafluoroethylene (PTFE), and fluorinated ethylene propylene (FEP)), partially fluorinated fluorocarbon polymers (including ethylene tetrafluoroethylene (ETFE), polychlorotrifluoroethylene (CTFE), ethylene-chlorotrofluoroethylene (ECTFE), and polyvinylidine fluoride (PVDF)), high performance engineering thermoplastics (including polyetheretherketone (PEEK)) and elastomeric perfluorocarbons (including elastomeric polytetrafluoroethylene) may be used, with PFA being preferred. These polymers reduce the amount of abraded particulate, are chemically inert, and provide a non-contaminating pressure transducer module.
In one embodiment of the pressure transducer module, the housing has a bore extending therethrough, which forms a passage or conduit through which fluids flow, when the transducer body is connected within a fluid flow circuit. Aligned and sealably connected to each open end of the bore are flared pressure fittings. The flared pressure fittings are constructed from a chemically inert material and are readily available and known to those skilled in the art. The housing also has a cavity extending from an external surface thereof in communication with the bore. A lip is preferably formed in the housing at the intersection of the cavity and bore. The lip has an inner dimension that is less than the inner dimension of the cavity. The isolation member, pressure sensor, electronic circuit, sealing member, spacer ring and hold down ring are all contained within the cavity of the housing in a manner described in greater detail below, wherein contamination of fluid within the fluid flow circuit is avoided.
The isolation member is sealed against the lip of the housing within the cavity. A ridge may be formed on the lip or an additional seal may be positioned on the lip between the lip and isolation member. In this manner, the cavity of the housing is sealed and isolated from the fluid flow. The isolation member is preferably constructed of an anti-corrosive, chemically inert material with perfluoroalkoxy being preferred. The pressure sensor is bonded, pressed, heat welded or otherwise engaging and adjoining the isolation member to provide intimate contact between the isolation member and the pressure sensor.
In an alternate embodiment, the pressure transducer module includes a removable tubular flexible isolation member that seals at the flared pressure fittings and extends through the bore. When fluids flow through the pressure transducer module, the isolation member is forced radially outward against the inner sides of the bore. The sensor may be positioned adjacent the cavity opening which intersects with the bore such that the sensor is adjacent and adjoins the isolation member. The thin tubular member effectively becomes an xe2x80x9cinvisiblexe2x80x9d barrier between the sensor and the fluid flow circuit.
In another embodiment the isolation member wraps around the lower surface and sides of the pressure sensor contained within a cavity of the pressure transducer module. Ridges or other sealing members in the cavity effectively seal the isolation member and sensor to the internal cavity. In this manner, the sensor may be positioned near or in the bore of the housing. A venting and sealing arrangement described below in detail, ensures that the UHP fluid flow is not contaminated by the pressure sensor extending into the bore or fluid flow.
The pressure sensor contained within the pressure transducer module may be of a suitable known construction, and more specifically may be of the capacitance, piezoresistive, or piezoelectric type. A hybrid or fully integrated electronic circuit disposed in the housing is operatively coupled to the pressure sensor and to the aforementioned connector. The electronic circuit develops a signal which corresponds to a measure of the pressure within the flow circuit from information sensed by the pressure sensor. This electronic circuit may also be used in combination with temperature sensitive components to adjust the pressure measurement based upon temperature changes within the flow circuit. As mentioned, the electronic sensor is coupled by electrical conductors to the electrical connector and power may be transmitted to the electronic circuit through the electrical connectors. Further, an analog output such as a standard 4-20 milliamps signal proportional to the calculated pressure may be transmitted through the connector to an external receiver.
It is accordingly a principal object of the present invention to provide a non-contaminating pressure transducer module connectable to a fluid flow circuit of UHP processing equipment.
Another object of the present invention is to provide a pressure transducer module wherein its pressure sensor component is isolated from the fluid flow circuit by a non-contaminating barrier wherein the affects of the barrier on the accuracy of the pressure measurement are negligible.
A further object of the present invention is to provide an interchangeable isolation member of a UHP processing equipment pressure sensor that may be replaced without contaminating the fluid flow circuit.
A still further object of the pressure invention is to provide a sealing arrangement that further isolates the pressure sensor from contact with fluids from the fluid flow circuit and prevents back flow of fluids back into the fluid flow circuit.
Yet another object of the present invention is to provide a pressure transducer module having an isolation member that is in direct contact and adjoining a pressure sensor, wherein the isolation member acts to isolate the sensor and associated electronic circuitry from potentially corrosive processing chemicals and precludes introduction of contaminating substances into the processing fluids being transported.
Still another object of the present invention is to provide a pressure transducer wherein a gauge pressure or absolute pressure of the flow circuit is measured nonintrusively.
These and other objects, as well as these and other features and advantages of the present invention will become readily apparent to those skilled in the art from a review of the following detailed description of the preferred embodiment in conjunction with the accompanying No claims and drawings in which like numerals in the several views refer to corresponding parts.
FIG. 1 is a perspective view of a pressure transducer module of the present invention;
FIG. 2 is a side elevational view of the pressure transducer module of the type shown in FIG. 1;
FIG. 3 is a partial sectional side elevational view of the pressure transducer module of the type shown in FIG. 1 having the cap removed;
FIG. 4 is an enlarged partial sectional side elevational view of the pressure transducer module shown in FIG. 3;
FIG. 5 is an enlarged perspective view of a flexible planar member suitable for use in the assembly of FIGS. 1 through 3;
FIG. 6 is a side elevational view of an alumina ceramic capacitive pressure sensor;
FIG. 7 is an enlarged partial sectional side elevational view of an alternate embodiment of the pressure transducer module of the present invention;
FIG. 8 is an enlarged partial sectional side elevational view of another alternate embodiment of the pressure transducer module of the present invention;
FIG. 9 is an enlarged partial sectional side elevational view of another embodiment of the pressure transducer module of the present invention;
FIG. 10 is an enlarged partial sectional side elevational view of another embodiment of the pressure transducer module of the present invention;
FIG. 11 is an enlarged partial sectional side elevational view of another pressure transducer module constructed in accordance with the present invention;
FIG. 12 is an enlarged partial sectional side elevational view of another embodiment of the pressure transducer module of the present invention;
FIG. 13 is an enlarged partial sectional side elevational view of another embodiment of the pressure transducer module of the type shown in FIG. 1;
FIG. 14 is an enlarged partial sectional side elevational view another embodiment of the pressure transducer module of the type shown in FIG. 1;
FIG. 15 is an enlarged partial sectional side elevational view of another embodiment of the pressure transducer module of the type shown in FIG. 1;
FIG. 16 is a side elevational view of another pressure transducer module constructed in accordance with the present invention;
FIG. 17 is a partial sectional side elevational view of the pressure transducer module of the type shown in FIG. 16;
FIG. 18 is a fragmentary partial sectional side elevational view of an alternate embodiment of the pressure transducer module of the type shown in FIG. 16;
FIG. 19 is a fragmentary partial sectional side elevational view of an alternate embodiment of the pressure transducer module of the type shown in FIG. 16;
FIG. 20 is a fragmentary partial sectional side elevational view of an alternate embodiment of the housing of the pressure transducer module in accordance with the present invention;
FIG. 21 is a fragmentary partial sectional side elevational view of an alternate embodiment of the pressure transducer module in accordance with the present invention;
FIG. 22 is a fragmentary partial sectional side elevational view of an alternate embodiment of the pressure transducer module in accordance with the present invention;
FIG. 23 is a partial sectional side elevational view of an alternate embodiment of the pressure transducer module in accordance with the present invention;
FIG. 24 is a fragmentary partial sectional side elevational view of an alternate embodiment of the pressure transducer module in accordance with the present invention;
FIG. 25 is a fragmentary partial sectional side elevational view of an alternate embodiment of the pressure transducer module in accordance with the present invention;
FIG. 26 is a fragmentary partial sectional side elevational view of an alternate embodiment of the pressure transducer module in accordance with the present invention;
FIG. 27 is a fragmentary partial sectional side elevational view of an alternate embodiment of the pressure transducer module in accordance with the present invention;
FIG. 28 is a fragmentary partial sectional side elevational view of an alternate embodiment of the pressure transducer module in accordance with the present invention;
FIG. 29 is a fragmentary partial sectional side elevational view of an alternate embodiment of the pressure transducer module in accordance with the present invention; and
FIG. 30 is a fragmentary partial sectional side elevational view of an alternate embodiment of the pressure transducer module in accordance with the present invention.